Trains were delayed this morning because of a "nationwide fault" with a communications system
The problem was caused by a new hardware card installed overnight and has been fixed, the BBC's transport correspondent Sean Dilley writes
Affected services included South Western Railway, Gatwick Express, Great Northern, Southern, Southeastern and Thameslink, plus lines across Wales
In Scotland, ScotRail earlier said it was affected - but later said services were running normally
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ScotRail earlier said on X , externalthat "services are subject to delays".
However the operator now says trains in Scotland are operating as normal.
ScotRail spokesman David Ross says information on apps and websites are updated by a UK-wide system, leading to incorrect information being displayed.
"When you check individual services things are operating normally," he says.
Meghan Owen
Reporting from Waterloo
Here at Waterloo, one woman tells me she will be three hours late for a job interview - adding there has been very little communication from the railway operators.
Scotrail says its services may be subject to delays as a result of the fault affecting the network this morning.
As we've been reporting, the issue relates to the radio system between drivers and signallers.
But the operator says the fault does not affect safety on services that do run, as "alternative methods are in place".
Meghan Owen
Reporting from Waterloo
The arrivals board at Waterloo shows several services disrupted this morning.
Commuters have told me they will be at least an hour late for work, and are having to plan alternative routes.
As we reported, National Rail says that there is a "nationwide" fault with the communication system used between train drivers and signallers.
According to National Rail, affected services include:
A "nationwide fault" is affecting rail services across the network, National Rail has said in a warning to rail passengers this morning.
The issue relates to the communication system used between train drivers and signallers, it says.
"Trains across the network are having to start their journeys later because of this fault and some may also be subject to cancellations or alterations," it says.
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